Conventionally, there is developed a technique of disposing an exhaust gas purification device (diesel particulate filter) in an exhaust path of a diesel engine so as to purify exhaust gas discharged from the engine by an oxidation catalyst, a soot filter, or the like of the exhaust gas purification device (see, for example, Patent Document 1). Further, in recent years, also in a field of work machines such as a construction machine or an agricultural machine, it is required to provide an exhaust gas purification device to a diesel engine used in the machine, as an environmental measure (see, for example, Patent Document 2).